I was reading this website ( https://pinyin.sogou.com/zimeiti/article/1255 ) to understand colloquial Beijing Mandarin and came across this pronunciation for 驾驶证
驾驶证 > "酱汁儿", i.e Jiàshǐ zhèng > jiàng zhī er
How should I understand these changes?
Is it something like 驾驶证儿, with shi disappearing in the middle (jia > jiang, shi> 0, zhengr > zhir), or is it 驾驶证 with shi becoming zhi and zheng becoming r (jia > jiang, shi> zhi, zheng > r)? I know ch, sh, and zh become r a lot but I also know whole syllables can disappear.